John Deere decks, 38" (old style three blade. new style two blade), 42" (newer deck), 44" (newer mulch/rear discharge), 46" (old deck), 48" (newer deck), 50" ( for 318/420, maybe a couple others), 54" (newer deck), 60" (both old and newer style), and lastly 72" (front mowers, sub compacts...